According to today's prior art, surfaces are mostly protected from corrosive influences and mechanical stress caused by friction by means of physisorbed thin liquid films (e.g. oils, waxes) or polymeric paints applied thereon. These conventional films usually have layer thicknesses in the range of a few micrometers up to millimeters. However, their exact layer thickness is difficult to control in terms of procedure.
Uncross-linked monolayers of the prior art, particularly those on the basis of aliphatic hydrocarbon chains, have a low mechanical stability and thus only provide an insufficient protective effect. Moreover, uncross-linked monolayers desorb upon contact with corrosive agents, since individual molecules at defective sites are displaced from the surface and the detachment of the layer continuous from those sites. Conventional methods for preparing such uncross-linked monolayers of organic molecules on different substrates are e.g. described in more detail in A. Ulman, “An Introduction to Ultrathin Films”, Academic Press, Boston 1991, as well as in A. Ulman, Chem. Rev. 1996, 96, 1533.
To solve these problems, DE-A-199 45 935 proposes a surface-modified layer system comprising a substrate and, at least partly disposed thereon, a monolayer composed of low-molecular aromatics and/or heteroaromatics, said monolayer being cross-linked in the lateral direction and covalently bonded to at least one surface of the substrate via anchor groups. The monolayer of these layer systems, which is composed of low-molecular aromatics and/or heteroaromatics and is cross-linked in the lateral direction, has the character of a cross-linked solid and thus protects the surfaces of corresponding substrates from being damaged by friction and corrosion. Such systems are particularly suitable for the surface protection of mechanically moved equipment with small working distances in the micro or nanometer range, such as hard disk drives for electronic data storage, or of micromechanical equipment with moved parts having dimensions in the micrometer range or below.
However, the disadvantage of these surface-modified layer systems is that they may have a lateral structure with respect to the cross-linkage by cross-linking with finely focused ionizing radiation or by using shadow masks, but that a monolayer cross-linked in the lateral direction has a uniform or homogenous surface, and thus no surface structure at all. It is therefore not possible to bond further nanoobjects to this cross-linked surface in a specific pattern.